Hello there.
I've got a TX3 Mini and trying to run LibreELEC / CoreELEC is really driving me crazy.
So I burn the .img from a release, copy a device tree to the root of the device, and change the *.dtb name to dtb.img, put the USB drive in a USB port, press and hold the reset button and then I plug the power cable to the TX3 Mini.
My USB drive has a led that blinks when being read/written to. It blinks briefly for three times, as trying to read something, but doesn't boot to LibreELEC. Tried many different .dtb files, but no luck.
I thought my box might not boot from USB, so I tried running Armbian for Amlogic, and running the aml_autoscript.zip "update.zip" I managed to boot to Armbian, run the initial configuration, but when it rebooted it went back to Android, with no more aml_autoscript.zip available to run.
Do you have any advices on what might be going on? Any chances that the chipset on my unit is different than S905W? How do I check it? I managed to install the LibreELEC x Android dual boot image, but the LibreELEC was too unstable to me: didn't manage to work with my MySQL database properly, the playback of 1080p content was not that smooth (my Raspberry Pi One does a better job), and so on.
Nevermind, it seems I was indeed using the wrong dtb, even though I tried many. The one that did the trick was gxl_p212_1g_tx3mini.dtb, from https://kszaq.libreelec.tv/s905/8.2/device_trees/s905x/ . Interestingly, even though it has 2GB (actually, I bought a 2 GB device and received a 1 GB one, that's what was wrong), the gxl_p212_2g_tx3mini.dtb device tree didn't seem to work.